/* Copyright  2009
   @Author
   Richard Changde Yin            e-mail yinchangde@hotmail.com

   This program is free software; you can redistribute it and/or modify
   it under the terms of the GNU General Public License as published by
   the Free Software Foundation; version 2 of the License.

   This program is distributed in the hope that it will be useful,
   but WITHOUT ANY WARRANTY; without even the implied warranty of
   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
   GNU General Public License for more details.

   You should have received a copy of the GNU General Public License
   along with this program; if not, write to the Free Software
   Foundation, Inc., 59 Temple Place, Suite 330, Boston, MA  02111-1307  USA */

/**
 *@filename:  hash.cc
 */

/* The hash functions used for saving keys */
/* One of key_length or key_length_offset must be given */
/* Key length of 0 isn't allowed */

#include <global.h>
#include CSTDINT_H
#include <hash.h>

const uint32_t NO_RECORD= UINT32_MAX;

const int LOWFIND= 1;
const int LOWUSED= 2;
const int HIGHFIND= 4;
const int HIGHUSED= 8;



static uint32_t hash_mask(uint32_t hashnr, uint32_t buffmax,
                          uint32_t maxlength);
static void     movelink(HASH_LINK *array, uint32_t pos,
                          uint32_t next_link, uint32_t newlink);
static int      hashcmp(const HASH *hash, HASH_LINK *pos,
                        const unsigned char *key,
                        size_t length);

static uint32_t calc_hash(const HASH *hash, const unsigned char *key,
                          size_t length)
{
  uint32_t nr1=1, nr2=4;
  hash->charset->coll->hash_sort(hash->charset, key,length, &nr1, &nr2);
  return nr1;
}

bool
_hash_init(HASH *hash,
           uint32_t growth_size,
           const CHARSET_INFO * const charset,
           uint32_t size,
           size_t key_offset,
           size_t key_length,
           hash_get_key get_key,
           hash_free_key free_element,
           uint32_t flags)
{
  hash->records=0;
  if (init_dynamic_array_ci(&hash->array, sizeof(HASH_LINK), size,
                               growth_size))
  {
    /* Allow call to hash_free */
    hash->free=0;
    return true;
  }
  hash->key_offset=key_offset;
  hash->key_length=key_length;
  hash->blength=1;
  hash->get_key=get_key;
  hash->free=free_element;
  hash->flags=flags;
  hash->charset=charset;
  return false;
}


/*
  Call hash->free on all elements in hash.

  SYNOPSIS
  hash_free_elements()
  hash   hash table

  NOTES:
  Sets records to 0
*/

static inline void hash_free_elements(HASH *hash)
{
  if (hash->free)
  {
    HASH_LINK *data=dynamic_element(&hash->array,0,HASH_LINK*);
    HASH_LINK *end= data + hash->records;
    while (data < end)
      (*hash->free)((data++)->data);
  }
  hash->records=0;
}


/*
  Free memory used by hash.

  SYNOPSIS
  hash_free()
  hash   the hash to delete elements of

  NOTES: Hash can't be reused without calling hash_init again.
*/

void hash_free(HASH *hash)
{
  hash_free_elements(hash);
  hash->free= 0;
  delete_dynamic(&hash->array);
  return;
}


/*
  Delete all elements from the hash (the hash itself is to be reused).

  SYNOPSIS
  hash_reset()
  hash   the hash to delete elements of
*/

void hash_reset(HASH *hash)
{
  hash_free_elements(hash);
  reset_dynamic(&hash->array);
  /* Set row pointers so that the hash can be reused at once */
  hash->blength= 1;
  return;
}

/* some helper functions */

/*
  This function is char* instead of unsigned char* as HPUX11 compiler can't
  handle inline functions that are not defined as native types
*/

static inline char*
hash_key(const HASH *hash, const unsigned char *record, size_t *length,
         bool first)
{
  if (hash->get_key)
    return (char*) (*hash->get_key)(record,length,first);
  *length=hash->key_length;
  return (char*) record+hash->key_offset;
}

/* Calculate pos according to keys */

static uint32_t hash_mask(uint32_t hashnr,uint32_t buffmax,uint32_t maxlength)
{
  if ((hashnr & (buffmax-1)) < maxlength) return (hashnr & (buffmax-1));
  return (hashnr & ((buffmax >> 1) -1));
}

static uint32_t hash_rec_mask(const HASH *hash, HASH_LINK *pos,
                              uint32_t buffmax, uint32_t maxlength)
{
  size_t length;
  unsigned char *key= (unsigned char*) hash_key(hash,pos->data,&length,0);
  return hash_mask(calc_hash(hash,key,length),buffmax,maxlength);
}



static
inline
unsigned int rec_hashnr(HASH *hash,const unsigned char *record)
{
  size_t length;
  unsigned char *key= (unsigned char*) hash_key(hash,record,&length,0);
  return calc_hash(hash,key,length);
}


unsigned char* hash_search(const HASH *hash, const unsigned char *key,
                           size_t length)
{
  HASH_SEARCH_STATE state;
  return hash_first(hash, key, length, &state);
}

/*
  Search after a record based on a key

  NOTE
  Assigns the number of the found record to HASH_SEARCH_STATE state
*/

unsigned char* hash_first(const HASH *hash, const unsigned char *key,
                          size_t length,
                          HASH_SEARCH_STATE *current_record)
{
  HASH_LINK *pos;
  uint32_t flag,idx;

  flag=1;
  if (hash->records)
  {
    idx=hash_mask(calc_hash(hash,key,length ? length : hash->key_length),
                  hash->blength,hash->records);
    do
    {
      pos= dynamic_element(&hash->array,idx,HASH_LINK*);
      if (!hashcmp(hash,pos,key,length))
      {
        *current_record= idx;
        return (pos->data);
      }
      if (flag)
      {
        /* Reset flag */
        flag=0;
        if (hash_rec_mask(hash,pos,hash->blength,hash->records) != idx)
          /* Wrong link */
          break;
      }
    }
    while ((idx=pos->next) != NO_RECORD);
  }
  *current_record= NO_RECORD;
  return(0);
}

/* Get next record with identical key */
/* Can only be called if previous calls was hash_search */

unsigned char* hash_next(const HASH *hash, const unsigned char *key,
                         size_t length,
                         HASH_SEARCH_STATE *current_record)
{
  HASH_LINK *pos;
  uint32_t idx;

  if (*current_record != NO_RECORD)
  {
    HASH_LINK *data=dynamic_element(&hash->array,0,HASH_LINK*);
    for (idx=data[*current_record].next; idx != NO_RECORD ; idx=pos->next)
    {
      pos=data+idx;
      if (!hashcmp(hash,pos,key,length))
      {
        *current_record= idx;
        return pos->data;
      }
    }
    *current_record= NO_RECORD;
  }
  return 0;
}


/* Change link from pos to new_link */

static void movelink(HASH_LINK *array, uint32_t find,
                     uint32_t next_link, uint32_t newlink)
{
  HASH_LINK *old_link;
  do
  {
    old_link=array+next_link;
  }
  while ((next_link=old_link->next) != find);
  old_link->next= newlink;
  return;
}

/*
  Compare a key in a record to a whole key. Return 0 if identical

  SYNOPSIS
  hashcmp()
  hash   hash table
  pos    position of hash record to use in comparison
  key    key for comparison
  length length of key

  NOTES:
  If length is 0, comparison is done using the length of the
  record being compared against.

  RETURN
  = 0  key of record == key
  != 0 key of record != key
*/

static int hashcmp(const HASH *hash, HASH_LINK *pos, const unsigned char *key,
                   size_t length)
{
  size_t rec_keylength;
  unsigned char *rec_key= (unsigned char*) hash_key(hash, pos->data,
                                                    &rec_keylength,1);
  return ((length && length != rec_keylength) ||
          my_strnncoll(hash->charset, rec_key, rec_keylength,
                       key, rec_keylength));
}


/* Write a hash-key to the hash-index */

bool hash_insert(HASH *info,const unsigned char *record)
{
  int flag;
  size_t idx;
  uint32_t halfbuff,hash_nr,first_index;
  unsigned char *ptr_to_rec=NULL,*ptr_to_rec2=NULL;
  HASH_LINK *data,*empty,*gpos=NULL,*gpos2=NULL,*pos;

  if (HASH_UNIQUE & info->flags)
  {
    unsigned char *key= (unsigned char*) hash_key(info, record, &idx, 1);
    if (hash_search(info, key, idx))
      /* Duplicate entry */
      return(true);
  }

  flag=0;
  if (!(empty=(HASH_LINK*) alloc_dynamic(&info->array)))
    /* No more memory */
    return(true);

  data=dynamic_element(&info->array,0,HASH_LINK*);
  halfbuff= info->blength >> 1;

  idx=first_index=info->records-halfbuff;
  /* If some records */
  if (idx != info->records)
  {
    do
    {
      pos=data+idx;
      hash_nr=rec_hashnr(info,pos->data);
      /* First loop; Check if ok */
      if (flag == 0)
        if (hash_mask(hash_nr,info->blength,info->records) != first_index)
          break;
      if (!(hash_nr & halfbuff))
      {
        /* Key will not move */
        if (!(flag & LOWFIND))
        {
          if (flag & HIGHFIND)
          {
            flag=LOWFIND | HIGHFIND;
            /* key shall be moved to the current empty position */
            gpos=empty;
            ptr_to_rec=pos->data;
            /* This place is now free */
            empty=pos;
          }
          else
          {
            /* key isn't changed */
            flag=LOWFIND | LOWUSED;
            gpos=pos;
            ptr_to_rec=pos->data;
          }
        }
        else
        {
          if (!(flag & LOWUSED))
          {
            /* Change link of previous LOW-key */
            gpos->data=ptr_to_rec;
            gpos->next= (uint32_t) (pos-data);
            flag= (flag & HIGHFIND) | (LOWFIND | LOWUSED);
          }
          gpos=pos;
          ptr_to_rec=pos->data;
        }
      }
      else
      {
        /* key will be moved */
        if (!(flag & HIGHFIND))
        {
          flag= (flag & LOWFIND) | HIGHFIND;
          /* key shall be moved to the last (empty) position */
          gpos2 = empty; empty=pos;
          ptr_to_rec2=pos->data;
        }
        else
        {
          if (!(flag & HIGHUSED))
          {
            /* Change link of previous hash-key and save */
            gpos2->data=ptr_to_rec2;
            gpos2->next=(uint32_t) (pos-data);
            flag= (flag & LOWFIND) | (HIGHFIND | HIGHUSED);
          }
          gpos2=pos;
          ptr_to_rec2=pos->data;
        }
      }
    }
    while ((idx=pos->next) != NO_RECORD);

    if ((flag & (LOWFIND | LOWUSED)) == LOWFIND)
    {
      gpos->data=ptr_to_rec;
      gpos->next=NO_RECORD;
    }
    if ((flag & (HIGHFIND | HIGHUSED)) == HIGHFIND)
    {
      gpos2->data=ptr_to_rec2;
      gpos2->next=NO_RECORD;
    }
  }
  /* Check if we are at the empty position */

  idx=hash_mask(rec_hashnr(info,record),info->blength,info->records+1);
  pos=data+idx;
  if (pos == empty)
  {
    pos->data=(unsigned char*) record;
    pos->next=NO_RECORD;
  }
  else
  {
    /* Check if more records in same hash-nr family */
    empty[0]= pos[0];
    gpos=data+hash_rec_mask(info,pos,info->blength,info->records+1);
    if (pos == gpos)
    {
      pos->data=(unsigned char*) record;
      pos->next=(uint32_t) (empty - data);
    }
    else
    {
      pos->data=(unsigned char*) record;
      pos->next=NO_RECORD;
      movelink(data,(uint32_t) (pos-data),
                    (uint32_t) (gpos-data),(uint32_t) (empty-data));
    }
  }
  if (++info->records == info->blength)
    info->blength+= info->blength;
  return(0);
}


/******************************************************************************
 ** Remove one record from hash-table. The record with the same record
 ** ptr is removed.
 ** if there is a free-function it's called for record if found
 *****************************************************************************/

bool hash_delete(HASH *hash,unsigned char *record)
{
  uint32_t blength,pos2,pos_hashnr,lastpos_hashnr,idx,empty_index;
  HASH_LINK *data,*lastpos,*gpos,*pos,*pos3,*empty;
  if (!hash->records)
    return(1);

  blength=hash->blength;
  data=dynamic_element(&hash->array,0,HASH_LINK*);
  /* Search after record with key */
  pos=data+ hash_mask(rec_hashnr(hash,record),blength,hash->records);
  gpos = 0;

  while (pos->data != record)
  {
    gpos=pos;
    if (pos->next == NO_RECORD)
      /* Key not found */
      return(1);

    pos=data+pos->next;
  }

  if ( --(hash->records) < hash->blength >> 1) hash->blength>>=1;
  lastpos=data+hash->records;

  /* Remove link to record */
  empty=pos; empty_index=(uint32_t) (empty-data);
  if (gpos)
    /* unlink current ptr */
    gpos->next=pos->next;
  else if (pos->next != NO_RECORD)
  {
    empty=data+(empty_index=pos->next);
    pos->data=empty->data;
    pos->next=empty->next;
  }

  /* last key at wrong pos or no next link */
  if (empty == lastpos)
    goto exit;

  /* Move the last key (lastpos) */
  lastpos_hashnr=rec_hashnr(hash,lastpos->data);
  /* pos is where lastpos should be */
  pos=data+hash_mask(lastpos_hashnr,hash->blength,hash->records);
  /* Move to empty position. */
  if (pos == empty)
  {
    empty[0]=lastpos[0];
    goto exit;
  }
  pos_hashnr=rec_hashnr(hash,pos->data);
  /* pos3 is where the pos should be */
  pos3= data+hash_mask(pos_hashnr,hash->blength,hash->records);
  if (pos != pos3)
  { /* pos is on wrong posit */
    empty[0]=pos[0];            /* Save it here */
    pos[0]=lastpos[0];          /* This should be here */
    movelink(data,(uint32_t) (pos-data),(uint32_t) (pos3-data),empty_index);
    goto exit;
  }
  pos2= hash_mask(lastpos_hashnr,blength,hash->records+1);
  if (pos2 == hash_mask(pos_hashnr,blength,hash->records+1))
  { /* Identical key-positions */
    if (pos2 != hash->records)
    {
      empty[0]=lastpos[0];
      movelink(data,(uint32_t) (lastpos-data),(uint32_t) (pos-data),empty_index);
      goto exit;
    }
    idx= (uint32_t) (pos-data); /* Link pos->next after lastpos */
  }
  else idx= NO_RECORD; /* Different positions merge */

  empty[0]=lastpos[0];
  movelink(data,idx,empty_index,pos->next);
  pos->next=empty_index;

exit:
  pop_dynamic(&hash->array);
  if (hash->free)
    (*hash->free)((unsigned char*) record);
  return(0);
}

/*
  Update keys when record has changed.
  This is much more efficient than using a delete & insert.
*/

bool hash_update(HASH *hash, unsigned char *record, unsigned char *old_key,
                 size_t old_key_length)
{
  uint32_t new_index,new_pos_index,blength,records,empty;
  size_t idx;
  HASH_LINK org_link,*data,*previous,*pos;

  if (HASH_UNIQUE & hash->flags)
  {
    HASH_SEARCH_STATE state;
    unsigned char *found,
      *new_key= (unsigned char*) hash_key(hash, record, &idx, 1);

    if ((found= hash_first(hash, new_key, idx, &state)))
    {
      do
      {
        if (found != record)
          return(1); /* Duplicate entry */
      }
      while ((found= hash_next(hash, new_key, idx, &state)));
    }
  }

  data=dynamic_element(&hash->array,0,HASH_LINK*);
  blength=hash->blength; records=hash->records;

  /* Search after record with key */

  idx=hash_mask(calc_hash(hash, old_key,(old_key_length ?
                                         old_key_length :
                                         hash->key_length)),
                blength,records);
  new_index=hash_mask(rec_hashnr(hash,record),blength,records);
  if (idx == new_index)
    return(0); /* Nothing to do (No record check) */
  previous=0;
  for (;;)
  {
    if ((pos= data+idx)->data == record)
      break;
    previous=pos;
    if ((idx=pos->next) == NO_RECORD)
      return(1); /* Not found in links */
  }
  org_link= *pos;
  empty=idx;

  /* Relink record from current chain */

  if (!previous)
  {
    if (pos->next != NO_RECORD)
    {
      empty=pos->next;
      *pos= data[pos->next];
    }
  }
  else
    previous->next=pos->next; /* unlink pos */

  /* Move data to correct position */
  if (new_index == empty)
  {
    /*
      At this point record is unlinked from the old chain, thus it holds
      random position. By the chance this position is equal to position
      for the first element in the new chain. That means updated record
      is the only record in the new chain.
    */
    if (empty != idx)
    {
      /*
        Record was moved while unlinking it from the old chain.
        Copy data to a new position.
      */
      data[empty]= org_link;
    }
    data[empty].next= NO_RECORD;
    return(0);
  }
  pos=data+new_index;
  new_pos_index=hash_rec_mask(hash,pos,blength,records);
  if (new_index != new_pos_index)
  { /* Other record in wrong position */
    data[empty] = *pos;
    movelink(data,new_index,new_pos_index,empty);
    org_link.next=NO_RECORD;
    data[new_index]= org_link;
  }
  else
  { /* Link in chain at right position */
    org_link.next=data[new_index].next;
    data[empty]=org_link;
    data[new_index].next=empty;
  }
  return(0);
}


unsigned char *hash_element(HASH *hash,uint32_t idx)
{
  if (idx < hash->records)
    return dynamic_element(&hash->array,idx,HASH_LINK*)->data;
  return 0;
}


/*
  Replace old row with new row.  This should only be used when key
  isn't changed
*/

void hash_replace(HASH *hash, HASH_SEARCH_STATE *current_record,
                  unsigned char *new_row)
{
  if (*current_record != NO_RECORD)            /* Safety */
    dynamic_element(&hash->array, *current_record, HASH_LINK*)->data= new_row;
}
